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Biomedical subjects

H Berg

Publications and source records attributed to H Berg.

At least 73 records · Page 4Linked to original sources
PubMed1983

Interaction of anthracycline antibiotics with biopolymers. VIII. Binding parameters of aclacinomycin A to DNA.

The binding of aclacinomycin A to DNA was investigated spectrophotometrically under equilibrium conditions. The self-association behaviour of aclacinomycin A was identified as dimerization. Based on a model of overlapping potential binding sites the subsequent results were obtained: equilibrium constant of cooperative binding K = (7.58 +/- 2.15) X 10(6) M(-1), size of a binding site alpha = 3.98 +/- 0.14 base pairs, cooperativity parameter sigma = 0.12 +/- 0.10. These parameters were compared with those of adriamycin, daunomycin, and iremycin to draw some conclusions regarding the structural specialities of aclacinomycin A.

Aclarubicin↗
PubMed1983

A mesophase (liquid crystal) state of DNA complexes with anthracycline antibiotics.

In the presence of polyethyleneglycol water-salt solutions, DNA is condensed to a kind of mesophase (liquid crystals). The peculiar properties of this phase caused by anisotropic orientations have been analyzed by circular dichroism (CD) of condensed particles of DNA complexed with dyes, i.e. anthracycline antibiotics (daunomycin, aclacinomycin A), actinomycin, and ethidium bromide. The anthracycline complexes show intense CD bands in the visible and the UV region. Daunomycin induces a typical reversal of the sign of these CD bands with increasing occupation of the double helix contrary to the other ligands. This characteristic effect and its partial reversal after removal of daunomycin from the condensed particles can be the result of the change of the direction of the mesophase helical twist owing to an energy change of interaction between DNA molecules, and partially to a modification of base-plane inclination (tilt), too. This new type of DNA complex state is characterized in detail.

Animals↗
PubMed1982

Circadian rhythm in urinary N-acetyl-beta-glucosaminidase (NAG) of clinically healthy subjects. Timing and phase relation to other urinary circadian rhythms.

Urinary N-acetyl-beta-glucosaminidase (NAG), a lysosomal enzyme of renal tubular origin, has been shown to be a sensitive indicator of renal tubular function. This study documents a circadian rhythm in the urinary activity of NAG, statistically validated and quantified by the cosinor method, in 19 female and 15 male human subjects. The acrophase of the circadian rhythm in urinary NAG activity occurs at 09(40) with 95% confidence limits between 08(40) and 12(08) and is similar to the timing of the circadian rhythm in urinary free cortisol. The circadian acrophase of urinary NAG activity lags in timing the circadian rhythms in urine volume, Na and K excretion, and urinary free adrenalin and noradrenalin, by about five to ten hours and the circadian rhythm in creatinine excretion by about 11 hours. These functions with their characteristic phase relations are part of the internal circadian time structure of the human organism, and may provide internal phase references, independent of the "time of day." This study also documents a sex difference in mesor of the circadian rhythms in urinary NAG activity, with female subjects having a higher mesor and amplitude than the male subjects, and in the excretion of creatinine and potassium, with male subjects having a higher mesor and amplitude than the female subjects.

Acetylglucosaminidase↗
PubMed1982

Electrochemical reduction pathways of anthracycline antibiotics.

The preparative electrochemical reduction of a series of anthracycline antibiotics was performed using the technique of large scale electrolysis and d. c. polarography for recording different reaction pathways. The reduction products were identified by mass spectrometric and chromatographic analyses. Only anthracyclines with sugar residues in the C-10 position chromatographic analyses. Only anthracyclines with sugar residues in the C-10 position (iremycin, roseorubicin A) were reduced reversibly by 2e- to the corresponding hydroquinones. All others with sugar residues in the C-7 position (daunomycin, 5-iminodaunomycin, adriamycin, carminomycin, beta-rhodomycin II, aclacinomycin A, 1-deoxypyrromycin) showed an irreversible behavior because of the reductive splitting of the glycosidic bond after formation of 7-deoxy compounds or -- if the C-11 OH-group was not present -- of dimers, respectively.

Anti-Bacterial Agents↗
PubMed1981

Two modes of longe-range orientation of DNA bases realized upon compaction.

Formation of compact particles from linear DNA-anthracycline complexes is accompanied by appearance of intense bands in the CD spectra in the region of absorption of DNA bases (UV-region) and in the region of absorption of anthracycline chromophores (visible region). The intense (positive or negative) bands in the region of anthracycline absorption demonstrate an ordered helical location of anthracycline molecules on the DNA template. This fact, in its turn, is related to formation of the DNA superstructure in PEG-containing water-salt solutions with a long-range orientation of nitrogen bases. Possible types of DNA superstructures and the relation between the local- and the long-range order of bases in the DNA superstructure are discussed.

Animals↗
PubMed1981

Microbiological implications of electric field effects. II. Inactivation of yeast cells and repair of their cell envelope.

The inactivation of yeast cells in different growth phases by an electric field pulse was investigated. Cells of Saccharomyces cerevisiae in the logarithmic growth phase were found to be much more sensitive with respect to an electric discharge than those in the stationary phase. The influence of the electric field pulse characteristics on the inactivation as well as possible secondary effects were studied. The polyene antibiotic perhydrohexafungin (PHF) is used as a tool to sense defects in the yeast cell envelope brought about by electric field action. The repair kinetics of these defects was followed after the impulse. At least two repair stages can be distinguished, a fast one in the second range and a slower one which takes place after plating the cells on a nutrient medium. The obtained results are discussed in connection with current theories of reversible dielectric breakdown in biological membrane systems.

Antifungal Agents↗
PubMed1981

Microbiological implications of electric field effects. III. Stimulation of yeast protoplast fusion by electric field pulses.

Prototrophic colonies could be selected on minimal medium after mixing of protoplasts from diauxotrophic mutants of the yeasts Saccharomycopsis lipolytica and/or Lodderomyces elongisporus and treatment with polyethylene glycol (PEG) in the presence of calcium chloride. This is the result of protoplast fusion and complementation of auxotrophic deficiencies. Under identical conditions an electric field pulse in the mus-range applied via an electric discharge to the protoplast-PEG mixture resulted in a drastic enhancement of the protoplast fusion rate. The presence of polyethylene glycol was demonstrated to be a prerequisite for fusion in this case, too. The frequency of hybrid formation detected a prototrophic colonies could be increased in the case of intraspecific fusion at initial electric field strengths between 2.5 and 5 kV . cm-1. The application of an electric field pulse of proper strength and duration to a yeast protoplast suspension turned out to be a more effective tool in production of fusion products that conventional methods. Large numbers of parasexual hybrids for different selection programmes in yeast genetics and for industrial purpose may be delivered by this technique.

Electricity↗
PubMed1980

The genetics of levamisole resistance in the nematode Caenorhabditis elegans.

We have characterized a small group of genes (13 loci) in the nematode Caenorhabditis elegans that, when mutated, confer resistance to the potent anthelmintic levamisole. Mutants at the 7 loci conferring the most extreme resistance generally possess almost identical visible and pharmacological phenotypes: uncoordinated motor behavior, most severe in early larval life, extreme resistance to cholinergic agonists and sensitivity to hypo-osmotic shock. Mutants with exceptional phenotypes suggest possible functions for several of the resistance loci. The most extreme mutants can readily be selected by their drug resistance (211 mutants, as many as 74 alleles of one gene). The more common resistance loci are likely to be unessential genes, while loci identified by only a few alleles may be essential genes or genes conferring resistance only when mutated in a special way. We propose that these mutants represent a favorable system for understanding how a small group of related genes function in a simple animal. The extreme drug resistance of these mutants makes them useful tools for the genetic manipulation of C. elegans. And, as the most resistant class of mutants might lack pharmacologically functional acetyl-choline receptors (LEWIS et al. 1980), these mutants may also be of some neurobiological significance.

Alleles↗
PubMed1977

Hepatocarcinogenetic effect of DENA in pigs.

DENA was fed to Göttingen mini-pigs at a dose of 0.4 mg/kg body weight with a total dosage of 420 mg/kg over an experimental period of five years. The animals showed multiple neoplasia of the liver with all transitions, including hepatocellular carcinoma and Kupffer-cell sarcoma with metastases in the regional lymph nodes and the lung. Two animals had metastases in the lung as well as one renal carcinoma and one tumor in the hemisphere of the brain.

Animals↗